Fossil fuels are major energy sources today and also serve as raw materials for various hydrocarbons and their derived products. However, fossil fuel reserves are on the decline.
An alternative to fossil fuels are geothermal energy sources. Geothermal energy sources provide hot water and steam and are increasingly used as alternative energy sources for generating electrical energy as well as for heating purposes. Hot water and steam are available as natural sources (geysers) or can be obtained by tapping (drilling) into suitable geological formations and pumping (passing) external water through them.
Geothermal energy sources and related geothermal wells usually also discharge carbon dioxide accompanying hot water or steam. Geothermal energy plants release carbon dioxide as a by-product in amounts from 2 to 40%, which is generally clean or can be readily purified by known methods. It has been until now usually vented into the atmosphere. Carbon dioxide can however be readily separated and used as a carbon source for the production of methanol and/or dimethyl ether, derived synthetic hydrocarbons and their products. The required hydrogen is generated from cleavage (electrolytic, thermal) of water using the heat or electricity produced by the same geothermal energy source.